Objectives-To measure the levels of exposure to nitrogen trichloride (NCl3) in the atmosphere of indoor swimming pools and to examine how they relate to irritant and chronic respiratory symptoms, indices of pulmonary function, and bronchial hyperresponsiveness to methacholine in lifeguards working in the pools.

Symptoms were assessed by questionnaire and methacholine bronchial challenge (MBC) test by an abbreviated method.

Subjects were labelled MBC+if forced expiratory volume in one second (FEV1) fell by =20%. The linear dose-response slope was calculated as the percentage fall in FEV, at the last dose divided by the total dose given.

Results

1262 samples were taken in the 63 pools.

Mean NCl3 concentrations were greater in leisure than in public pools.

A significant concentration-response relation was found between irritant eye, nasal, and throat symptoms-but not chronic respiratory symptoms-and exposure concentrations.

Among women, the prevalence of MBC+was twice as great as in men.

Overall, no relation was found between bronchial hyperresponsiveness and exposure.

Conclusions-The data show that lifeguards exposed to NCl3 in indoor swimming pools are at risk of developing irritant eye, nasal, and throat symptoms. (...)